The invention is directed to a crystalline zeolite powder of Type A having the composition EQU 1.0.+-.0.2M.sub.2/n O:Al.sub.2 O.sub.3 :1.85.+-.0.5SiO.sub.2.yH.sub.2 O
wherein M is a metal cation, e.g., sodium, potassium, lithium, calcium, magnesium or barium, n its valence and y has a value up to 6 with 50 weight % of the particles not over 4.3.mu. and a process for the production of the crystalline zeolite powder by means of a hydrothermal crystallization of an alkali aluminate silicate mixture, as well as its use in washing, rinsing and cleansing agents.
Zeolite molecular sieves and their special properties for ion exchange and adsorption have been known for a long time. Their synthesis depends on heating an aqueous synthesis mixture with the components a Na.sub.2 O.times.b Al.sub.2 O.sub.3 .times.c SiO.sub.2 to a temperature between 50.degree. and 300.degree. C. According to the composition of the starting mixture, reaction temperature and reaction time there are obtained different structured compounds of the general formula EQU Na.sub.x Al.sub.x Si.sub.y O.sub.2(x+y).nH.sub.2 O
which are distinguishable by their X-ray spectra. Sodium can be replaced by other mono- and divalent metal cations, e.g., potassium, lithium, cesium, magnesium, barium and strontium.
For use as adsorption agents, catalyst carriers or ion exchangers the molecular sieves are converted into molded articles with a suitable binder. The production of the molded article means a great industrial expense with simultaneous reduction of the effect because of the binder component. Also, because of the long diffusion path, the reaction speed is greatly retarded, which, e.g., makes cumbersome the drying of organic liquids. It is, therefore, significant to add molecular sieve powders in many uses.
The known processes of production (e.g., Milton German Pat. No. 1,038,017 and Milton U.S. Pat. No. 2,882,243) have in common that crystals are obtained in the molecular sieve synthesis whose average diameter is above about 2.mu., whereby a considerable portion, customarily between 3 and 12 weight % have a border grain (limiting particle) diameter above 45.mu.. This portion is designated grit; it is ascertained by DIN 53580 (German Industrial Standard 53580) by wet sieving according to Mocker. In a typical product for this process, it has been ascertained that about 25 weight % of the particles have a diameter below 10.mu., 50 weight % have a particle diameter below 13.mu. (D. W. Breck, Zeolite Molecular Sieves, page 388 (1974)).
The invention is based on the problem of creating a process of synthesizing and providing a powdery zeolitic molecular sieve of Type A having a samller particle size without formation of grit components (particles &gt;45.mu.), which molecular sieve is especially useful as an ion exchange, e.g., for water softening. The absence of grit as well as a smaller particle size is indispensable for a number of uses within the invention, e.g., use of such molecular sieves, e.g., as phosphate replacements in washing, rinsing and cleansing, processes. Washing, rinsing and cleansing processes, especially in machines, imply indeed a lasting suspension of the molecular sieve (as a result of a slight tendency for quiescent setting) in the liquor in order to make possible a residue free rinsing after completion of the process.